Conventional self-powered machine gun feed mechanisms are typically of the reciprocating transverse variety. This type of mechanism incorporates a feed lever, generally located near the top of the weapon, which pivots in a rather large feed cover and tray member. As the bolt carrier reciprocates it moves the feed lever back and forth. The feed lever actuates a pawl which advances belted rounds of ammunition to the feed position. The rounds are held in this position by another pawl, which is also controlled by the feed lever. This is a complex mechanism consisting of many moving parts, springs, etc. For example, there are 75 parts in the feed mechanism of the M60 machine gun now in use. Obviously a mechanism of this type would be more susceptible to failure or breakage than one containing fewer parts.
Another disadvantage of this prior art system is that the feed cover is pivotally mounted at its forward end and must be pivoted upward in order to load or clear the weapon. This is a shortcoming because, from the prone position, a gunner would have to expose too much of himself to accomplish the loading or clearing function, to his possible detriment.